Method and apparatus that modifies seeks to remediate inter-actuator coupling in a storage drive

ABSTRACT

A faulty tracking condition affecting a first head driven by a first actuator of a hard disk drive is determined. The faulty tracking condition is caused by a second actuator of the hard disk drive that is moving while the first actuator is performing a tracking operation. Responsive to the determination of the faulty tracking condition, seek forces of the second actuator that cause the faulty tracking condition affecting the first head are reduced. A controller verifies that similar faulty tracking conditions are reduced with the first head in response to the reduction in seek forces.

SUMMARY

The present disclosure is directed to a method and apparatus thatmodifies seeks to remediate inter-actuator coupling in a storage drive.In one embodiment, a faulty tracking condition affecting a first headdriven by a first actuator of a hard disk drive is determined. Thefaulty tracking condition is caused by a second actuator of the harddisk drive that is moving while the first actuator is performing atracking operation. Responsive to the determination of the faultytracking condition, seek forces of the second actuator that cause thefaulty tracking condition affecting the first head are reduced. Acontroller verifies that similar faulty tracking conditions are reducedwith the first head in response to the reduction in seek forces.

These and other features and aspects of various embodiments may beunderstood in view of the following detailed discussion and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The discussion below makes reference to the following figures, whereinthe same reference number may be used to identify the similar/samecomponent in multiple figures.

FIG. 1 is a block diagram of an apparatus according to an exampleembodiment;

FIG. 2 is a flowchart of a method according to an example embodiment;

FIG. 3 is a block diagram of faulty tracking condition criteriaaccording to an example embodiment;

FIG. 4 is a block diagram showing remedial actions to reduce seek forcedisturbances according to an example embodiment;

FIG. 5 is a flowchart showing an open-loop control procedure accordingto an example embodiment;

FIG. 6 is a flowchart showing a closed-loop control procedure accordingto an example embodiment; and

FIG. 7 is a block diagram of an apparatus according to an exampleembodiment.

DETAILED DESCRIPTION

The present disclosure generally relates to data storage devices thatutilize magnetic storage media, e.g., hard disk drives (HDDs).Additional HDD features described herein, generally described as“parallelism” architectures are seen as a way to improve HDD performancemeasures such as TOPS and latency. Generally, parallelism architecturesutilize multiple read/write heads in parallel. Such parallelism canincrease the rate of input/output operations (IOPS) and thereby speed upcertain operations. For example, the data read from two heads can becombined together into a single stream, thereby doubling the throughputrate of data sent to the host. In other examples, different heads canservice different read or write requests at the same time, therebyreducing overall latency, e.g., for random data access requests. In someembodiments, using two heads simultaneously involves operating twoactuators (e.g., voice coil motors) at the same time as well.

The simultaneous seek capability of a multiple actuator disk drive isnot without technical implementation challenges. There are variousdifferent mechanical approaches to multiple actuators, such as twoactuators collocated on a common pivot axis, or two actuators locatedapart (e.g., opposed) on different pivots. Regardless of whichmechanical approach is taken, seek performance can be affected by themechanical interactions between actuators. When an actuator isaccelerated and decelerated, it imparts equal and opposite forces on thedrive enclosure. These forces are felt by the other actuators in thesystem and are compensated for during their tracking and seeking by aservo control system.

The greatest forces intentionally exerted during normal operation areduring seek acceleration and deceleration of the actuators. These forcesare most likely to impact the ability to track settle and track followon the other actuator(s). The largest impact to performance is causedwhen settle and follow operations during writing are disturbed. Thesettle/follow constraints are tighter during writing so as not toaccidently overwrite adjacent track data. If these operations aredisturbed too much, then the write operation will be delayed orsuspended resulting in degraded performance.

In embodiments described below, a controller is configured to reduceforces induced by seeks of one actuator when the other actuator(s) areeither observing a high rate of late seeks and/or write faults and/or isin a state that is very susceptible to increased disturbances. Thisallows adjusting performance during drive operation such that theperformance of one actuator can be reduced (e.g., less aggressive seeks)in order to improve the performance of another actuator (e.g., reducedelayed or missed writes).

In FIG. 1, a diagram illustrates an apparatus 100 with parallelismfeatures according to example embodiments. The apparatus 100 includes atleast one magnetic disk 102 driven by a spindle motor 104. A head 106(also referred to as a read/write head, read head, write head, recordinghead, etc.) is held over a first surface 102 a of the disk 102 by an arm108. An actuator 114 moves (e.g., rotates) the arm 108 to place the head106 over different tracks on the disk 102. The actuator 114 may includea voice coil motor (VCM) that rotates in response to an electricalcurrent, although embodiments described herein may be applicable toother tracking actuators, e.g., linear actuators, microactuators, etc.

In one embodiment, the head includes a read transducer 110 and/or awrite transducer 112. The read transducer 110 provides a signal inresponse to changing magnetic fields on the disk 102, and is coupled toa controller 132, where the separate read signals are independentlyprocessed. The write transducer 112 receives signals from the controller132 and converts them to magnetic fields that change magneticorientations of regions on the disk 102.

The apparatus 100 includes a second head 116 supported by a second arm118. The second head 116 is held over a second surface 102 b of the disk102 and actuator 114 causes the second arm 118 to move to differenttracks on the disk 102. The arm 118 may move together with arm 108, orthe arms 108, 118 may move independently (as indicated by dashed line onactuator 114 indicating a split VCM actuator). In either configuration,the arms 108, 118 rotate around the same axis. The head 116 alsoincludes read and/or write transducers 120. The transducers 120 arecapable of reading from and/or writing to disk surface 102 bsimultaneously with one or both of read/write transducers 110, 112 thataccess disk surface 102 a.

In another embodiment, the apparatus 100 includes a third head 126supported by a third arm 128. The third head 126 (and its associatedactuation hardware) may be included instead of or in addition to thesecond head 116. The third head 126 is held over the first surface 102 aof the disk 102 as a second actuator 124 causes the third arm 118 tomove to different tracks on the disk 102. The arm 128 and actuator 124move independently of arm 108 and actuator 114. The head 126 includesread and/or write transducers 130. The transducers 130 are capable ofreading from and/or writing to disk surface 102 a simultaneously withtransducers 110, 112 of first head 106. The second actuator 124 mayoptionally include another arm that accesses second surface 102 b of thedisk 102.

In the examples shown in FIG. 1, more than one disk 102 may be used, andthe actuators 114, 124 may be coupled to additional heads that accesssome or all of the additional disk surfaces. In this context,“accessing” generally refers to activating a read or write transducerand coupling the transducer to a read/write channel. Independentlymovable heads that utilize a split actuator 114 may generallysimultaneously access different surfaces, e.g., heads 106 and 116 accessdifferent surfaces 102 a, 102 b at the same time. Independently movableheads that utilize non-coaxial actuators 114, 124 may access the samesurface at the same time, e.g., heads 106 and 126 may both accesssurface 102 a at the same time, as well as accessing different surfacesat the same time. The arms 108, 118, 128, 129 may also includemicroactuators 134-137 that control fine movements of the heads. Themicroactuators 134-137 may include motive elements such piezoelectricstrips that undergo small deformations in response to an appliedelectrical current.

One or more controllers 132 are coupled to the respective actuators 114,124 and control movement of the actuators 114, 124 and microactuators134-137. The controllers 132 may include one or more ASICs orsystems-on-a-chip (SoCs) that perform parallel operations such as servocontrol, encoding and decoding of data written to and read from the disk102, queuing and formatting host commands, etc. Where two or more ASICsor SoCs are used, the ASICs/SoCs may have identical hardware (e.g.,formed from the same semiconductor die pattern), although may beconfigured to perform differently, e.g., due to different firmwareand/or software instructions that are executed at start up.

In any of the mechanical approaches illustrated in FIG. 1, one effect ofhaving independently operating actuators are the interactions betweenactuators. When an actuator is accelerated and decelerated, it impartsequal and opposite forces on the drive structure. These forces are feltby the other actuators in the system. If not compensated for duringtracking and seeking, these reaction forces can reduce performance ofthe other actuators, e.g., increase settling times, cause mistracking,result in undershooting or overshooting a target track, etc.

In FIG. 2, a flowchart illustrates a high-level procedure for mitigatinginter-actuator interference according to an example embodiment. Acriterion is set 200 that indicates a likelihood of cross-actuatorinterference that impacts performance. In response to the criterionbeing met, a seek parameter (e.g., acceleration or deceleration current,types and timing of seek operations) of another actuator that likelycaused the cross-actuator interference is modified 201. After themodification 201, the affected actuator is monitored to verify 202improvement due to the modification 201. This verification 202 can beimmediate, e.g., in a closed-loop controller which measures changesright after changing the seek parameter, or over long-term use, e.g., inan open-loop controller that makes occasional adjustments responsive tolong-term trends.

A number criteria can be used separately or in combination to determinethat the seek forces should be reduced by one or more of the actuatorsas shown in block 200 of FIG. 2. A number of these criteria are shown inthe block diagram of FIG. 3. As shown in blocks 300 and 301, onecriteria which may be applicable to both read and/or write operations ofthe affected head is a percentage of seeks completing past expectedposition, e.g., greater than a predetermined threshold value, e.g.,fixed value or one that can vary over time. Blocks 302 and 303 indicatecriteria that are also applicable to reads and writes of the affectedhead, and relate to percent seeks completing past expected positiongreater than an average value plus an offset. The offset may be constantor variable (e.g., changes as the drive ages). For blocks 300-303,accumulated excess time (actual minus expected) may be monitored insteadof percentage of seeks past target position. This accumulated time valuemay be used, either alone or divided by the total number of seeks.

Blocks 304-308 represent write-only criteria to determine disturbancesof an affected head from the seeking of another actuator. The criterionin block 304 is percent writes by the affected head that encounter anoff-track write fault that are greater than a predetermined fixed orvariable threshold value. The criterion in block 305 is percent writesof the affected head encountering an off-track write fault that aregreater than an average value plus an offset (e.g., constant or variableoffset). The criterion in block 306 is write fault frequency of theaffected head being greater than a fixed or variable threshold value.Generally write fault frequency refers to the ratio of write faults tototal number of write operations. The criterion in block 307 is writefault frequency being greater than an average value plus a constant orvariable offset. The criterion in block 308 is percent of recent timethe affected head spends in susceptible mode (e.g., write settlingand/or write track following) greater than a fixed or variable thresholdvalue.

Note that any of the criteria 300-308 may be combined to form acomposite criterion of susceptibility to disturbance from anotheractuator. The criteria may be expanded, e.g., applying some criteria304-308 to read operations. The susceptibility may vary for differentmodes of operation (e.g., read, write) thus combining them may involveweighting of each term. Note that the threshold values and offsetsdescribed above may change over time, e.g., due to expected or measuredchanges in device operation due to wear. Such thresholds and offsets maybe also or instead dynamic values that change based upon operatingconditions, such as operational vibration, temperature, humidity, driveorientation, power saving modes, etc.

Generally, once a criteria or combination thereof indicate possibilityor likelihood of a significant inter-actuator disturbance, seek forcesof at least the actuator suspected of causing the disturbances arereduced. In FIG. 4, a block diagram shows a number of techniques thatmay be used to reduce inter-actuator interference according to exampleembodiments. These techniques are generally described as remedialactions, in that they are intended to reduce negative impacts on otheractuators and heads in the storage device. The remedial actions may bemade in any combination, and may be applied short- or long-term toongoing drive operations.

As indicated by block 400, one remedial action involves reducing theseek acceleration forces of the disturbance-causing actuator. Forexample, the maximum allowable acceleration of the actuator may bereduced. As seen in blocks 401 and 402, which represent accelerationcurves versus time before and after remediation, the peak accelerationis reduced, although the time spent accelerating may increase, and otherfactors may be adjusted, e.g., time to start accelerating may beearlier. This can reduce seek forces induced by acceleration whileminimizing impacts to seek time.

As indicated by block 404, another remedial action involves reducing thedeceleration forces of the disturbance-causing actuator. For example,the maximum allowable acceleration of the actuator may be reduced. Asseen in blocks 405 and 405, which represent deceleration curves versustime before and after remediation, the peak deceleration is reduced,although the time spent decelerating may increase, and other factors maybe adjusted, e.g., time to start decelerating may be earlier. This canreduce seek forces induced by deceleration while minimizing impacts toseek time.

As indicated by block 408, another remedial action involves reducingboth the acceleration and deceleration forces of the disturbance-causingactuator. For example, the maximum allowable acceleration of theactuator may be reduced. As seen in blocks 409 and 410, which representacceleration curves versus time before and after remediation, the peakacceleration and deceleration is reduced, although the time spentaccelerating and decelerating may increase. Other factors may beadjusted, e.g., time to start accelerating/decelerating may be earlier.Note that the reduction may be asymmetric, e.g., the acceleration isreduced more or in a different way than the acceleration or vice versa.

The changes to acceleration and/or deceleration may generally involvereshaping the seek current profiles in a manner that reduces seek forceswhile minimizing the impact to seek times. As shown in block 412, thereduction of pulse width seek currents, as seen in blocks 413, 414, canbe used to reduce accelerations and decelerations. As shown in block416, another way to reduce actuator forces is to alter the commandscheduling policy to favor commands that induce less seek forces. Asseen in blocks 417 and 418, for example, the change in schedulingresults on more low-disturbance seeks and fewer high-disturbance seeks.Similarly, accesses with long latencies can be identified and scheduledappropriately allowing the servo system to slow seekacceleration/deceleration without further access-time penalty.

In order to compensate for inter-actuator coupling, a number of controlmechanisms may be used. For example, an open-loop controller may be usedthat, upon detecting one or more criteria as shown in FIG. 3, reducesseek forces or performs other actions such as shown in FIG. 4. Theamount of reduction may be scaled based on the magnitude or type ofdetection criteria. Upon detecting that criteria no longer exists, thedevice reverts to normal seek operation or modifying the scaling factorof the reduction. Detecting the criteria exists or no longer exists mayinvolve some hysteresis and/or time lag. Using an open-loop controlmechanism causes minimal interruption in the normal operation of thedevice, although may not be able to react as quickly as other controlmechanisms.

In FIG. 5, a flowchart shows an open-loop control procedure according toan example embodiment. This procedure may be performed for each targetset of heads associated with a target actuator. In such a case, thedisturbance criteria are associated with the target set of heads, andthe remedial actions are associated with and performed on actuatorsother than the target actuator.

At block 500, time tracking and a remedial action state variable areinitialized, and normal read/write operations are performed at block501. The time tracking variable represents the value that tracks systemand/or operational time, the timer being reset by setting the variableto zero. Block 502 checks the timer variable against a time threshold.Block 502 may be entered in response to a polling mechanism, timerinterrupt, or other computing process/mechanism that relates to time,and/or may be triggered by a tracking error that is considered part ofthe performance criteria analyzed at block 503. Assuming the timevariable meets or exceeds the threshold (block 502 returns ‘yes’), acheck is made to see if one or more performance criteria are met as seenin block 503 e.g., block 503 returns ‘yes’ if performance is negativelyimpacted. It may be assumed that during normal operations performed inblock 501, tracking and other errors as shown in FIG. 3 are continuallylogged such that the criteria can be evaluated before or at the decisionat block 503 occurs.

If the one or more disturbance criteria are not met (block 503 returns‘no’), a check at block 504 is made to see if a remedial action iscurrently being applied. If so, then the current remedial action isremoved and the state variable reset as shown in block 505.Alternatively, instead of removing the remedial action, the remedialaction may be altered. For example, if remedial actions are scaled(e.g., maximum acceleration reduced by a scaling factor n<1) so onepossibility so to change the scaling (maximum acceleration reduced by ascaling factor m, where n<m<1). In either case, the timer is reset asshown in block 506. If the one or more disturbance criteria are met(block 503 returns ‘yes’), a check at block 507 is made to see if aremedial action is currently being applied. If not (block 507 returns‘no’), then remedial action is begun, and the timer and remedial actionstate variables are reset as shown in block 508. The remedial actionstarted at block 508 may include any combination of action shown in FIG.4.

Note that if block 507 returns ‘yes,’ then the remedial action iscurrently being applied, but the disturbance is still affecting thetarget head(s) such that block 503 still returns ‘yes.’ This case isdemonstrated by block 509, which shows one example of what can be donein this case. As shown in block 509, an alternate remedial action may beselected, and then treated the same as the previous remedial action viablock 508. The alternate remedial action may be a different mechanism orcombination of mechanisms (e.g., altering scheduling versus reducingacceleration and/or deceleration) and/or may involve scaling thecurrently used remediating mechanisms. As indicated by the dashed linefrom block 509, an alternate choice may be to remove or scale anyexisting remedial action, in which case control passed to block 505. Insuch a case, the existence of the disturbance may be logged, and otheractions may be taken, e.g., sending an alert via drive status reportingmechanisms that communicate with the host.

Another control mechanism that may be used in a drive to effect theabove-indicated remediation is closed-loop control. For example, upondetecting a disturbance criteria in a closed-loop controller, seek forcereduction or other actions are performed. The amount of reduction may bescaled based on detection criteria. While in the state of reduced seekforces, the criteria is actively monitored. If insufficient improvement,allow seek forces to be increased or potentially reverting to normalseek operation. If improvement and detection criteria (possibly alteredfrom original criteria to enter this mode) still indicates an issue,seek forces may be further reduced, or other actions may be performed(e.g., change schedule, send alert to host).

In FIG. 6, a flowchart shows a closed-loop control procedure accordingto an example embodiment. As with the open-loop procedure shown in FIG.5, the closed-loop procedure in FIG. 6 may be performed for each targetset of heads associated with a target actuator. In such a case, thedisturbance criteria are associated with the target set of heads, andthe remedial actions are associated with and performed on actuatorsother than the target actuator.

Block 600 represents normal operation of the drive, e.g., reading andwriting data to the recording medium. In response to a trigger or othermechanism monitored during this operation (e.g., read error, writeerror, etc.), a check is made as shown at block 602 to see ifdisturbance criteria is met. If so, then iteration through a loop beginsat block 603 that attempts to reduce or eliminate the disturbance. Atblock 603, a loop counter variable is initialized and remedial action isbegun, e.g., some combination of actions as shown in FIG. 4. Thebeginning of the loop is block 604.

At block 604, performance of the target head or heads are monitoredunder test conditions and/or normal operating conditions, e.g.,executing a number of currently queued commands. In the latter case, thequeued commands may be selected in an order designed to replicate thedetected disturbance rather than the default queueing order. During thismonitoring, disturbance criteria is tested as indicated at block 605. Ifthe currently selected remediation is effective, then block 605 willreturn ‘no’ and normal operations can commence. If block 605 returns‘yes,’ then the remediation was not successful. Before altering theremedial action at block 607, the counter is checked at block 606 to seeif it exceeds a threshold times through the loop. In such a case, theremedial action may be removed as indicated at block 608, and normaloperations commence. Note other actions may be performed at block 608,such as applying the most effective remediation action found in the loopeven if it didn't meet the criteria. Error logging and reporting mayalso occur.

At block 607, the current remedial action is changed, and the loopcounter is incremented. The changing of remedial action may involveusing a different mechanism or combination of mechanisms (e.g., alteringscheduling versus reducing acceleration and/or deceleration) and/or mayinvolve scaling the currently used remediating mechanisms. After thechange, the performance is again immediately evaluated at block 604, andthis continues until either the disturbance is sufficiently reduced viablock 605 or the loop limit is met via block 606.

In FIG. 7, a block diagram illustrates a data storage drive 700 thatutilizes one or more actuators according to example embodiments. Theapparatus includes circuitry 702 such as one or more device controllers704 that process read and write commands and associated data from a hostdevice 706 via a host interface 707. The host interface 707 includescircuitry that enables electronic communications via standard busprotocols (e.g., SATA, SAS, PCI, etc.). The host device 706 may includeany electronic device that can be communicatively coupled to store andretrieve data from a data storage device, e.g., a computer, a server, astorage controller. The device controller 704 is coupled to one or moreread/write channels 708 that read from and write to surfaces of one ormore magnetic disks 710.

The read/write channels 708 generally convert data between the digitalsignals processed by the device controller 704 and the analog signalsconducted through two or more heads 712, 732 during read operations. Thetwo or more heads 712, 732 each may include respective read transducerscapable of concurrently reading the disk 710, e.g., from the samesurface or different surfaces. The two or more heads 712, 732 may alsoinclude respective write transducers that concurrently write to the disk710. The write transducers may be configured to write using aheat-assisted magnetic recording energy source, and may write in varioustrack configurations, such as conventional, shingled, and interlaced.

The read/write channels 708 may include analog and digital circuitrysuch as digital-to-analog converters, analog-to-digital converters,detectors, timing-recovery units, error correction units, etc. Theread/write channels 708 coupled to the heads 712, 732 via interfacecircuitry 713 that may include preamplifiers, filters, etc. As shown inthe figure, the read/write channels 708 are capable of concurrentlyprocessing one of a plurality of data streams from the multiple heads712, 732.

In addition to processing user data, the read/write channels 708 readservo data from servo marks 714 on the magnetic disk 710 via theread/write heads 712, 732. The servo data are sent to one or more servocontrollers 716 that use the data to provide position control signals717 to one or more actuators, as represented by voice coil motors (VCMs)718. The VCM 718 rotates an arm 720 upon which the read/write heads 712are mounted in response to the control signals 717. The position controlsignals 717 may also be sent to microactuators (not shown) thatindividually control each of the heads 712, e.g., causing smalldisplacements at each read/write head.

The VCM 718 may be a stacked or split actuator, in which case two VCMparts are configured to independently rotate different arms about acommon axis 719. In such a case, other heads (not shown) will accessdata on the disks simultaneously with that of heads 712, and these otherheads may be coupled to circuitry 702 similar to illustrated head 732.In other embodiments, a second actuator, e.g., VCM 728, mayindependently and simultaneously rotate a second arm 730 about a secondaxis 729. Corresponding heads 732 may be rotated by the VCM 728 and mayoperate simultaneously with the heads 712 under commands from the one ormore servo controllers 716.

A disturbance mitigation module 740 is operable via the controller 704and can access a data store 742. This data store 742 may includedisturbance criteria and parameters of possible or currently implementedremedial actions as described above, or equivalents thereof. Thedisturbance mitigation module 740 may, for example, determine a faultytracking condition affecting a first head 712 driven by a first actuator718 of the hard disk drive 700. The faulty tracking condition of theaffected head 712 is caused by a second actuator 728 of the hard diskdrive 700 moving while the first actuator 718 is performing a trackingoperation. Seek forces of the second actuator 728 are reduced after thefaulty tracking condition. The module thereafter verifies (e.g., usingclosed-loop or open-loop control) that similar faulty trackingconditions are reduced or do not occur with the first head 712responsive to the reduction in seek forces.

The various embodiments described above may be implemented usingcircuitry, firmware, and/or software modules that interact to provideparticular results. One of skill in the arts can readily implement suchdescribed functionality, either at a modular level or as a whole, usingknowledge generally known in the art. For example, the flowcharts andcontrol diagrams illustrated herein may be used to createcomputer-readable instructions/code for execution by a processor. Suchinstructions may be stored on a non-transitory computer-readable mediumand transferred to the processor for execution as is known in the art.The structures and procedures shown above are only a representativeexample of embodiments that can be used to provide the functionsdescribed hereinabove.

The foregoing description of the example embodiments has been presentedfor the purposes of illustration and description. It is not intended tobe exhaustive or to limit the embodiments to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. Any or all features of the disclosed embodiments can beapplied individually or in any combination are not meant to be limiting,but purely illustrative. It is intended that the scope of the inventionbe limited not with this detailed description, but rather determined bythe claims appended hereto.

What is claimed is:
 1. A method, comprising: determining a faultytracking condition affecting a first head driven by a first actuator ofa hard disk drive, the faulty tracking condition caused by a secondactuator of the hard disk drive that is moving while the first actuatoris performing a tracking operation: responsive to the determination ofthe faulty tracking condition, reducing seek forces of the secondactuator that cause the faulty tracking condition affecting the firsthead; and verifying that similar faulty tracking conditions are reducedwith the first head responsive to the reduction in seek forces.
 2. Themethod of claim 1, wherein verifying that similar faulty trackingconditions are reduced with the first head comprises an open-loopcontrol procedure that involves: returning to normal operation afterreducing the seek forces; and determining, in response to a trigger,whether the similar faulty tracking conditions are reduced.
 3. Themethod of claim 2, wherein the determining whether the similar faultytracking condition occurs is further in response to an elapsed timesince a previous similar determination occurred exceeds a timethreshold.
 4. The method of claim 1, wherein verifying that similarfaulty tracking conditions are reduced with the first head comprises aclosed-loop control procedure that involves: actively monitoring a testoperation or normal operation after reducing the seek forces; anddetermining, in response the active monitoring, whether the similarfaulty tracking condition occurs.
 5. The method of claim 4, wherein theclosed-loop control procedure further involves iteratively changing aremedial action that reduces the seek forces and determining whether thesimilar faulty tracking conditions are reduced in response to thechange.
 6. The method of claim 1, wherein reducing seek forces of thesecond actuator applied to the first actuator comprises reschedulingoperations of the second actuator to mitigate the faulty trackingcondition, the rescheduling reducing long seeks of the second actuator.7. The method of claim 1, wherein reducing the seek forces comprisesreducing one of an acceleration and deceleration of the second actuatorduring seeks by the second actuator.
 8. The method of claim 1, whereinreducing the seek forces comprises reducing both of an acceleration anddeceleration of the second actuator during seeks by the second actuator.9. The method of claim 1, wherein the reduction of the seek forces isscaled based on at least one of a magnitude and a type of the faultytracking condition.
 10. The method of claim 1, wherein the determiningof the faulty tracking condition comprises determining that an excessivenumber of seeks of the first actuator past an expected position haveoccurred.
 11. The method of claim 1, wherein the determining of thefaulty tracking condition comprises determining that an excessive numberof off-track write faults have occurred.
 12. The method of claim 1,wherein the determining of the faulty tracking condition comprisesdetermining that an excessive time spent in susceptible mode by thefirst head has occurred.
 13. The method of claim 1, wherein thedetermining of the faulty tracking condition comprises determining aweighted combination of number of off-track write faults, number ofseeks of the first actuator past an expected position, and time spent insusceptible mode by the first head.
 14. A data storage drive comprising:interface circuitry coupled to first and second actuators that driverespective first and second heads that read one or more disks; and acontroller coupled to the interface circuitry and operable to: determinea faulty tracking condition affecting the first head caused by thesecond actuator moving while the first actuator is performing a trackingoperation: responsive to the determination of the faulty trackingcondition, reduce seek forces of the second actuator that cause thefaulty tracking condition affecting the first head; and verify thatsimilar faulty tracking conditions are reduced with the first headresponsive to the reduction in seek forces of a hard disk drive, thefaulty tracking condition caused by a second actuator.
 15. The datastorage drive of claim 14, wherein the determining of the faultytracking condition comprises determining any combination of a number ofoff-track write faults, a number of seeks of the first actuator past anexpected position, and a time spent in susceptible mode by the firsthead.
 16. The data storage drive of claim 14, wherein reduction of theseek forces comprises any combination of rescheduling operations of thesecond actuator to reduce long seeks, reducing an acceleration and ofthe second actuator during seeks, and reducing a deceleration of thesecond actuator during the seeks.